Thermocouple



ian 25, 1927 r, R. HARRISON THERMOCOUPLE 2 Sheets-Sheet 1 Filed Feb. l,1926 @4f/M@ ATTORNEY l Jan. 25, i927 T. R.- HARRISONV THERMOCOUPLE FiledFeb. l. 1926 -2 Sheets-Sheet 2 r1- w fr A MSM TW l@ Qwb xNb )VG INVENTORPatented Jan. 25;, i927.

'rIIoMAs n. HARRISON, or PHILADELPHIA, PENNSYLVANIA, AssIGNoR 'ro THEBROWN INSTRUMENT COMPANY, OPPIIILADELPIIIA, PENNSYLVANIA, Acon- PORATIN0F PENNSYLVANIA.

THEIuNocoUPLE.

Application mea February 1, 192e. seri'ai No. 85,176.

The general object of the present invention is to provide simple andeffective means for protecting thermo-couples employed in measuring thehigh furnace temperatures from injurious contact with vthe furnacegases. Heretofore serious troubles have ,been experienced as a resultofthe der teriorating action of furnace gases on the l thermo-coupleconductors both when the thermo-couple elements are the so-called noblemetals employed in measuring high furnace temperatures as for example inburning refractories where' the thermo-couple may be exposed to furnacetemperatures as high as 27 O0 F. or above, orare the base' metalsemployed in measuringtemperatures not higher than 180()o F. orthereabouts. In thermo-couples employed under such conditions the activeportions of the thermo-cuple conductors, including the hot junction ofthe thermo-couple are commonlyT surrounded by a tube or casing ofnon-metallic material such as unglazed porcelain, fire clay, oranalogous material, the purpose of such tube or casing being to preventthe furnace, gases from coming into contact with the thermo-coupleconductors. In practice, however, when such a protective tube be-.conies highly heated in use, furnace gases frequently pass through thepores of, or through cracks in the. protective tube in amount suiiicientto corrode'and destroy or impair the effectiveness of the thermo couple.

In accordance' with the present invention, thermo-couples for measuringhigh furnace temperatures are protected against injurious contact withfurnace gases in a simple and practically feasible manner, bymaintainingv a minute ow of air through the interior of the protectivecasing of theI thermo-couple. This flow of air must be relativelyminute' in quantity to prevent it fromhaving anyappreciable orsignificant cooling 'eifect which would make the thermo-coupleindications A lower than vthey should be, but only a very minute flow'of airl through the thermo-couple casing is required to eliminate theinjurious consequences of' furnace gasj leak# age into thethermo-couple. casing. To secure the desired How of `air through thethermo-couple casing, I may employ the furnace` draft, as by providingan outlet connection from the thermo-couple casing to a portion of thefurnace in which a minus pressure exists while at the same timeprovlding an in-` let to the casing for atmospheric air which is suckedthrough the casing by the furnace draft suction; In lieu of using thefurnace draft suction in this manner, any other suitable and convenientaspiratlng means may be employed. For instance, 1n some cases I mayprovide a thermo-couple casing with a vertical outlet pipe extendingupward from the thermo-couple casing along the outer wall of the furnaceand open at its topto the atmosphere so that the heat of the furnacecoupled with the heat absorbed by the thermo-couple 'casing will providea stack action giving the-necessary draft.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and formingy apart of this application. For a better understanding of the invention,

however. its advantages and specific objects.

attained with its use, reference -should be had to the accompanyingdrawings and descriptivematter'in which I have illustrated and describedpreferred embodiments of my invention.

Of the drawings: Fig. 1 is a sectionalV elevation of la. portion of afurnaceand thermo-couple for measuri ing the temperature therein;

Fig. 2 is an enlarged section of the mo-couple shown in Fig. 1;

Figs. 3. 4, 5, and 6 2are views taken similarly to Fig. 2 eachillustrating a different modification.

In the drawings and referring first to Figs. 1 4and 2, A represents thewall of a furnace. Into ahigh temperature portion which as shown inFigs. 1 and 2, comprises united at B to form a hot junction and conther-A of its interior extends a thermo-couple, l

nected at their .opposite .ends to the usual terminals provided'Y in thethermo-couple head C. The two elements B which are encased and separatedbysuitable refractory insulating material D, -are surrounded by aporcelain or analogous tube E having its inner end closed and its outerend connected to` ed into a socket formed for the purpose in f Athe headC, and a cement packing F between the metal tube F and the casing E. The

outer end of the casing E is openA to a chamber C' in the head C sealedfrom the external atmosphere by the terminal support ing plate C2 exceptfor a fine inlet port C8 through which atmospheric air may enter thechamber C and pass into the space within the casing E surrounding theinsulated' 'elements B which do not fill the casing E.

nected by -a pipe G to the furnace chamber A as shown in Fig. 1, whereina pressure yless than that of the atmosphere is assumed to exist. l

With the arrangement shown in Flg. 1, the furnace draft suctiontransmitted to the inner end of the casing E through the pipes G and G,draws atmospheric air into the chamber C in thethermo-couple head Cthrough the port C3. and thence through the casing E to the inner end ofthe latter from which the air passes into theopeu inner'end of the tubeG. The air flow thus set up through the casing tube E and out ot thelatter through the tube G carries with it any furnace gas passingthrough the pores of, or cracks in the porcelain tube E, and only arelatively minute stream of air is required to prevent a furnace gascontent in the atmosphere surrounding. the thermocouple elelnents Bsuliiciently large to make 4that atmosphere injurious to thethermocouplel elements. In particular', the flow of air requiredtoprevent injurious contamination of the atmosphere surrounding thethermo-couple elements need and should not be large enough to have anysignificant cooling action on the hot junction B of the thermo-couple.The cross sectional areas ot' the passages, and particularly the bore ofthe'inlet passage C8 and of the pipes G or G should be made small enoughrelativel to the furnace draft suction so as to keep the air flowthrough the thermo-couple casing suitably small.

Various modifications of the apparatus shown in Figs. 1 and '2 may bemade, and some'of these are shown by way of example 1n Flgs. 3, 4, 5,and 6. The arrangement shown in Fig. 3 differs from that shown i-n Fig.1, merely in that the thermoscouple elements B and their insulation Dare 4enclosed in a separate casing tube H having a closed vinner end andordinarily formed ofv `Which may leak through the pores of, or cracksinthe tube H is not a furnace gas atmospherc, but an atmosphere of airadmixed with a small portion only of the furnace,-

gases which may leak through the tube E.

The arrangement shown in Fig. 4 differs from that shown in Figsl, 2, and3, in that the pipes G and G' are dispensed with, and in lieu thereof asmall port E is formed in the inner end of the casing tube E, so thatthe furnace draft suction draws atmospheric air into the chamber C', andthence through the port C, tube E, and port E into the furnace chamber.As shown' in Fig. 4, thc casing H is centrallydisposed in the casing Eand is supported at its outer end by a iiange or cross head part H.

The arrangement shown in Fig. 5 dill'ers from that shown in Fig. 4 inthat atmospheric air entering the portion of the chamber C at the outerside of thc cross head or flange portion H through a port C10, is drawnthrough the member H to the inner end of the latter and thence through aport `H2 in the inner end of the casing member H. into the space betweenthe casing member H and surrounding casing E, the air then passing bachthrough said space to the portion of the chamber Cat the inner side ofthe flange or cross head portion Il and escaping through the outlet pontC.l The voutlet port C may be connected to the interior ol the 'furnacechamber with which the thermo-couple is used by a pipe similar to thepipe G oliFigs., 1, 2, and 3, but as shown. the port C11 is connected tothe lower. end of an uprising pipe G2 which is adapted to serre as asort of a stack or chimney for producing the .desired flow 0f airthrough the thern'io-couple casing. The stack draft created by the pipeG2, may obviously beI augmented by locating the pipe G2 adjacent the hotouter Wall of the furnace with which the thermo-couple is used so as tothereby increase the temperature and decrease the density of the columnof air in the pipe G2.

The arrangement shown in' Fig. 5v ossesses the advantage over theconstructions previously referred to, in that an increase in furnacechamber gas pressure cannot cause the furnace gases to back up in thethermocouple 'casing through the pipe G2, as they may through the pipe Gof Figs.v1, 2, and 3. or through the port E of Fig. 4.

' It will be understood, of course, that the thermo-couple casing andhead may vary in form rfrom those illustrated in FigsQl to 5. Forexample, as shown in Fig. 6, the head CA may be provided with a supportC21 for a bushing C22 which surrounds and supports the outer end of theinner thermo-couple casing H, and closes the outer end of the4 casing E.In Fig. 6 the terminal support C20 is formed With an aperture C23 topermit atmospheric air to. enter the outer end of the member H which isformed-at its inner end with a port H2 opening into the c surroundingspace within the casin member Air is drawn out of the annu ar space4between the ca'sing members E and4 H through a port C2* formedin thebushing C22 into the chamberCz5 in the head CA to which a pipev G visconnected as in the constructions shown in Figs. 1, 2, and 3. lt

will be understood further that while in suparatus disclosed withoutdeparting from the spirit of my invention as set forth lin the appendedclaimsand that in some cases certain features of my invention may be`used to advantage Without a corresponding use of other features.

-Having now described my invention what I claim as new and desire tosecure'byLetf ters Patent is;

LA thermo-couple comprising thermocouple conductors and a casingreceiving said conductors and provided with means .forming a path of-low for a stream of air adapted to sweep4 out noxious gases leaking"'ifnto said casing.

2. In a. thermo-couple for measuring high temperatures, the combinationwith thermocouple conductors united to form a hot ]unction. of anelongated casing formed a longitudinally extending chamber receivingsaid yconductors and having one closed end 4adjacent. which said hotjunction is located,

and means providing an aircliannel within,

and extending longitudinally of said casing and communicating withV saidchamber adjacent'its closed 'endg 3.A A thermo-couple comprisingthermocouple conductors and an elongated casing receiving said'conductors and provided with means forming a iow pathand'means forcreating an air flow along said ath adapted to sweep out noxious gaseslea 'ng through saidgases.

4. The combination with thermo-couple conductors united to form ahot'junction, of an elongated casing formed'with a longitudinallyextending chamber in which said conductors are received and having oneclosed end adjacent which said hot junction is located, means providingan air channel within and extending longitudinally of said casing and incommunication with said chamber adjacentaits closed end, and means forcreating an air flow longitudinal of said casing in one directionthrough said chamber andin the oppositedirection through said channel.

5. The combination with a furnace, of a thermo-couple extending into thefurnace and comprising thermo-couple conductors and a refractoryprotective casing forsaid conductors, and means for utilizing thefurnace draft to create a small air flow through said casing to therebyprotect said conductors against injury from furnace gases leak- 'ingthrough saidcasing. g

- Signed atV Philadelphia, in the countyof Philadelphia. and State ofPennsylvania,

this 29th day of January, A. D.l 1926.

THOMAS R. HARRISON.

